How to set up HEART Communication with the PLC by using Solidot EhterNet/IP Slice I/O

Left: 693000 EtherNet/IP Slice I/O Coupler XB6S-EI2002

Middle: Shidian Technology EtherNet/IP Integrated I/O (vertical) EI4-0016A

Right: Shidian Technology EtherNet/IP Integrated I/O (horizontal) EI3-3200

In the field of industrial automation, the approach of pairing a PLC with remote I/O has become increasingly widely used. To ensure the stability and reliability of communication, the Heartbeat Mechanism method is usually adopted, which plays an important role in monitoring the connection status during communication.

I. Heartbeat Mechanism principle

The Heartbeat Mechanism monitors the communication status by periodically sending variable data or high/low level signals. This involves a concept called the heartbeat address, which is a variable — typically a Boolean or integer type.

II. Implementation method

1. Monitor the EtherNet/IP Coupler status word

Currently, among Shidian Technology's EtherNet/IP protocol products, only the Slice I/O type has the Coupler status word function. Take XB6S-EI2002 as an example —

The coupler has two status words that occupy the first two word addresses of the input data. When communication is normal, the status words are 0 and 0 respectively.

Simply monitoring whether the status words are 0 and 0 to determine normal communication is unreliable, because after going offline or freezing, the status word data is not refreshed and remains at 0 and 0.

Therefore, in the program, we can periodically write other values to the two status word addresses every 1 s, for example writing 5 and 5 respectively. When CR2006 is OFF, the status words are 0 and 0; when CR2006 is ON, the status words are overwritten to 5 and 5; when CR2006 turns OFF again, the status words automatically refresh back to 0 and 0, and this cycle repeats. When the monitored status words are not 0 and 0 for more than 1 s, it can be determined that the slave is offline or that there is a general Coupler fault as shown below —

When CR2006 is OFF, the status words are 0 and 0:

When CR2006 is ON, the status words are 5 and 5:

2. Periodic DO triggering of DI signal Edge Transition Since Shidian Technology's EtherNet/IP protocol Integrated I/O products in the EI3 and EI4 series do not have the status word function, the only option is to periodically use DO to trigger a DI signal Edge Transition. When the PLC monitors that the DI signal has not changed for a long time, it can be determined that the slave is offline.

The above is a detailed introduction to the implementation method of the Heartbeat Mechanism for communication between a PLC and Shidian Technology's EtherNet/IP protocol I/O. If you have any questions, please feel free to contact us — we will be happy to assist you!